<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        /* .list::after{
            content: '';
            clear: both;
            display: block;
        } */
        .list{
            overflow: hidden;
        }
        li{
            width: 300px;
            height: 100px;
            float: left;
        }
        li:nth-child(1){
            background-color: aqua;
        }
        li:nth-child(2){
            background-color: red;
        }
        li:nth-child(3){
            background-color: green;
        }
        /* .title::before{
            content: '$$$$$'
        } */
        /* .title{
            clear: both;
        } */
    </style>
</head>
<body>

    <ul class="list">
        <li>1</li>
        <li>2</li>
        <li>3</li>
    </ul>

    <h2 class="title">
        <span>hello</span>
    </h2>

</body>
</html>